In today's complex technical society, government and private workers are frequently asked to perform rigorous and difficult tasks requiring precise motor skills, concentration, and manual dexterity. Workers ranging from trained operators on high speed mass transit lines to research scientists in high technology laboratories must consistently perform with the maximum of their intellectual and motor skills in order to safely and efficiently accomplish their jobs. Unfortunately, today many sensory altering temptations exist which can cause people to temporarily, permanently, or progressively lose the full use of their mental faculties. Narcotics, opiates, depressants, stimulants, alcohol, and both legal and illegal drugs may produce deleterious and destructive effects on an individual's mental and physical performance.
The effects of these substances can be dramatic and oftentimes dangerous to the individual under their influence, and to a public that depends on that individual to be performing adequately. Drug and alcohol abuse have recently been responsible for highly publicized devastating plane and train accidents, and doubtless numerous other smaller catastrophes which have not been reported by the media. Additionally, both government and private industry suffer billions of dollars of yearly losses due to inefficiency, absenteeism, and waste by individuals that are impaired by, or under the influence of, legal and illegal substances which alter their sensory perceptions.
Key segments of society, such as the military, transportation industries, and other private employers are severely burdened with the growing costs that drug and alcohol abuse wreak on worker productivity, and employee and public safety. Conservative estimates report that the annual cost of lost productivity and employment due to drug abuse is 26 billion dollars per year, and for alcohol abuse is 54.7 billion dollars per year. The insurance industry estimates that the cost of injuries, accidents, lost employment and crime due to drug abuse is about 85 billion dollars per year. The United States Chamber of Commerce and the National Institute on Drug Abuse (NIDA) estimate the cost to the national business community due to drug abuse in the workplace may be as much as one hundred billion dollars per year, but when non-business impacts are included in the cost, it may be closer to 200 billion dollars per year.
There has therefore been great emphasis placed by government and private employers in developing and implementing drug control programs, employee assistance programs for drug abuse, and pre-employment drug and alcohol testing. When the high number of sensitive positions are considered in the Departments of Defense, Transportation, Energy, and others, as well as the high number of important positions in private industry, the need for comprehensive, cost-effective, and efficient drug and alcohol impairment testing becomes apparent. All of the aforementioned government and industrial players, are highly concerned by these problems, and have been involved in instituting various kinds of drug and alcohol testing for their employees with an eye towards reducing and eliminating drug and alcohol abuse.
To date, there have been a number of subjective evaluations and objective tests created and implemented which detect alcohol and drug intoxication. The more common definitive objective tests are urine and blood tests (collectively referred to as "body fluid" tests) and, in the case of the impaired motorist, breath tests to determine potential blood alcohol levels and intoxication. Body fluid tests generally require obtaining a sample of an individual's urine or blood and having the urine or blood chemically analyzed to determine the quantitative level of drugs or alcohol in the body. Such body fluid testing has been used for several decades by the police, the military, and corrections officials to identify illegal drug and substance abusers.
Today, the market for sample acquisition and collection for all types of body fluid drug-related testing, processing, and laboratory analysis including report preparation is estimated to be about 750 million dollars per year, with a projected growth rate of about 15-20% through the mid-1990s. However, this projected growth rate will depend on the acceptance of random body fluid testing which is currently under attack by legal challenges related to invasion of privacy, chain of custody issues, and general Fourth Amendment rights. These attacks illustrate a general lack of confidence which both the scientific and legal communities ascribe to body fluid testings. This lack of confidence is a direct result of the inherent unreliability and non-repeatability of body fluid testing in determining impairment.
Furthermore, the cost of body fluid testing is prohibitive for all but the largest companies and governmental agencies. For example, the laboratory analysis costs of an individual two-step urine test that validates positive drug levels with a mass spectrometer is between $35-60. Coupling this cost with the management costs of body fluid testing techniques, which is generally far greater than the analytical test itself because of the need to comply with new government regulations embodied in, for example, 49 C.F.R. .sctn..sctn.40, 217, 219, 225, 391, 199; 14 C.F.R. 1, and .sctn.121; and 46 C.F.R. .sctn.16, the total costs to an employer can range from $200 to $560 per test. Since to be effective body fluid tests must be repeated often, they present a significant financial burden to companies and government agencies that are required to periodically test their workers.
Because body fluid testing exhibits both prohibitive costs and questionable accuracy, efforts have been made to develop other ways to test for drug and alcohol impairment. These efforts generally approach the solution to this problem through the use of non-invasive, non-intrusive methods that utilize electronics and computer equipment to perform the testing. Many types of instruments have been developed for this purpose. One such instrument is the video electronystagmograph disclosed in U.S. Pat. No. 4,815,839, Waldorf.
The Waldorf patent discloses a system for viewing and recording eye movement. See Waldorf, col. 1, lines 7-11. In particular, the Waldorf patent teaches a system which views and records the vertical, horizontal and rotary eye movement of a subject. When a subject is impaired or is suffering from certain diseases, he or she may exhibit "nystagmus" which is a jerky movement of the eyeball. The Waldorf device detects such nystagmus.
However, there has not been clinical confirmation, nor does the Waldorf patent disclose, that nystagmus monitoring is useful in detecting drug or alcohol impairment. No quantitative or qualitative data exists which definitively explains the relationship between nystagmus and various responses to individuals under the influence of opiates, alcohol or other types of drugs. Therefore, the video electronystagmographs disclosed in the Waldorf patent fail to solve a long-felt need in the art for an efficient and accurate apparatus which performs substance impairment testing.
A general class of instruments for measuring pupil diameter and responses have been developed which are called "pupillometers." A pupillometer measures, displays and records pupil diameter before and after a light stimulus causes a constriction and redilation of the pupil. Early results published in W. B. Pickworth et al., "Opiate Induced Pupillary Effects on Humans, "Methods and Findings in Experimental, Clinical Pharmacology, 1989, Vol. 11, pgs. 759-763, indicate that opiates cause systematic changes in the dynamic pupillary responses in humans and that measurement of these changes may be useful in a quantitative estimate of drug-induced impairment. Furthermore, it has been determined that opiates cause dose-related decreases in pupil size and decreases in the velocity of constriction and dilation of the pupil following a light stimulus. NIDA has thus determined that pupillometers in drug abuse treatment settings and basic research laboratories will offer efficient methods of assessing exposure to psychoactive drugs. See A. Radzius et al., "A Portable Pupillometer System for Measuring Pupillary Size and Light Reflex," Behavior Research Methods, Instruments and Computers, 1989, 21(6) 611-618.
At the present time, laboratory pupillometers have been developed to study pupil size and reactivity as indicators of central nervous system activity directly related to the body's reaction to external stimuli such as light, and internal stimuli such as drugs, alcohol, fatigue, anxiety, and psychopathic states. Additionally, pupillometry has been used over the past twenty years in clinical research for diagnosing various symptoms in anesthesiology, diabetology, trauma assessment and, most recently, in measuring psycoaddictive drug effects and other substance abuses. However, advances in pupillometry have been hampered because technicians and medical personnel have had to depend strictly upon bulky, difficult to use, and unreliable instruments that require a high level of operating skill. Many types of prior pupillometers have also been extremely costly.
Other kinds of pupil diameter measuring instruments have been developed which use high speed close-up cameras, video cameras, and infrared pupillometers. Prior infrared pupillometers offering automatic data reduction and analysis are bulky, cumbersome, unreliable, and cost between $30,000 and $150,000 for a single instrument. These instruments also generally have limited automatic data analysis features and may require cumbersome analysis of data which is time consuming and inefficient.
However, the advantages of pupillometers outweigh the advantages of body fluid tests which have heretofore been used to indicate drug or alcohol impairment. Pupillometers provide immediate, real time, and direct indication of impairment due to neurological compromise which has been shown to cause altered pupil size, and degraded pupil response to external stimulus. Thus, pupil response indicates impairment due to medications and illegal drugs. Additionally, pupillometer readings can be done in a low cost, repetitive environment and exhibit from tens to hundreds of times the reduction in cost compared to the costs of body fluid tests. Such advantages have not been fully realized, since there has yet to be developed an efficient and accurate pupillometer to perform alcohol or drug impairment testing because of the aforementioned problems that exist with prior pupillometers.
An example of a prior pupillometer can be found in U.S. Pat. No. 4,850,691, Gardner et al. The Gardner et al. patent discloses a method and apparatus for determining pupillary response with minimum effects from artifacts. See Gardner et al., col. 5, lines 1-27. The Gardner et al. patent further teaches a pupillometer comprising a means for establishing a dark field condition around the eye, and means within the dark field for irradiating the eye before pupil measurements are made. Measurements with pupillometers disclosed in the Gardner et al. patent require the storing of a quiescent level of radiation and irradiating the eye with a pulse of visible light to make comparisons of the reflections of the visible light with the quiescent radiation before the pupil size can be determined. These functions are accomplished by a number of electronic amplifiers and storage devices adapted to perform data manipulation and control. Furthermore, independent electronic instrumentation is required to perform the pupil measurements discussed in the Gardner patent. See Gardner, col. 7, lines 28-63.
The Gardner et al. patent discloses a complex and cumbersome machine which requires the use of a significant amount of costly computer hardware and instrumentation before pupil measurements are obtained. Furthermore, the device taught in the Gardner et al. patent makes pupil size measurements as a function of time in the form of a difference signal which is inaccurate and encourages the detection of artifacts, which is highly undesirable. The pupillometer disclosed in Gardner et al. cannot adequately eliminate errors produced by artifacts since the pupillary light response monitor taught therein is strongly affected by ambient light which has not been removed with the goggles that cover the subject's eyes. Thus the pupillometer disclosed in the Gardner et al. patent does not satisfy a long-felt need in the art for a pupillometer which efficiently performs pupil size measurement. Furthermore, the Gardner et al. pupillometer cannot perform adequate drug impairment testing because of the aforementioned infirmities apparent from its construction.
Other pupillometers have been developed and are disclosed in, for example, U.S. Pat. No. 4,755,043, Carter. The Carter patent discloses a portable, automatic scanning pupillometer for inspecting holes and gaps, for example a pupil, of up to about 10 millimeters in diameter. See Carter, col. 1, lines 51-66. The Carter patent further teaches a pupillometer which comprises a hand-held optical unit for measuring and stimulating the pupil, and supporting electronics mounted on a main processor circuit board wherein operating software is stored on an EPROM chip. An external computer may be used to control the hand-held device. Furthermore, the Carter patent teaches that an operator of the pupillometer, usually a technician trained to test a subject, must focus a reticle marked with concentric circles through an eyepiece to center the pupil image so that pupil scanning can occur.
While the hand-held pupillometer disclosed in the Carter patent provides an excellent optical system for measuring pupil response, it fails to provide efficient pupillometry which can be used for drug and alcohol impairment testing because it does not stabilize the subject's head, does not provide a focussing point for the subject to stabilize the eyes, and does not provide a stable measuring platform. The Carter pupillometer thus requires extensive practice by an independent technician to achieve efficient use and is not a self-measurement device. Rather, the pupillometer disclosed in the Carter patent must be aligned by the technician, rather than the subject. However if a technician is not adequately trained in the use of the devices, or the subject is uncooperative or under any influence of drug or alcohol, the complicated alignment protocol required by the Carter pupillometer will not allow for efficient and time-effective pupillometric measurements. Furthermore, the Carter patent does not disclose or teach an alignment system with appropriate software enhancements to provide ease of operation, especially for non-technical users.
There therefore exists a long-felt need in the art for self-measuring, portable electronic pupillometers which may be used for efficient and economical determinations of drug or alcohol impairment. This need has not been solved by any of the prior devices discussed above. The novel features, operation and advantages of methods and apparatus provided in accordance with the present invention will be better understood in light of the aforementioned problems, and further in view of the detailed description of preferred embodiments read in conjunction with the accompanying drawings.